Details

The category tree may be a general tree which would contain:

A Products root, just like the current category tree.
A Manufacturers root, it would work with manufacturers just like the category tree + product listing.
A Currencies root, it would work with currencies just like the category tree + product listing.
A Taxes root, just like the category tree + product listing.

In the future it would include Orders and Attributes.

We already load the whole Manufacturers list, Currencies and Taxes.

The product listing would change to a manufacturer, currency and taxes listing.

However, currently, with the product listing, we load the whole product descriptions and metadata when a category is selected. With manufacturers, currencies and taxes, I think we can load the whole set each time the user start using that part of the tree.

Maybe currencies, taxes and manufacturers would not require children nodes in the category tree, as they are not hierarchical data.

This would be such a huge improvement in the user interface usability. I am setting the priority of this to High.